feat: add comprehensive devcontainer setup and update README

Author: egyjs

.devcontainer/devcontainer.json

@@ -0,0 +1,29 @@
+{
+  "name": "OpenAgentFlow Starter Dev Container",
+  "image": "mcr.microsoft.com/devcontainers/python:3.11-bookworm",
+  "features": {
+    "ghcr.io/devcontainers/features/node:1": {
+      "version": "22"
+    },
+    "ghcr.io/devcontainers/features/git:1": {}
+  },
+  "customizations": {
+    "vscode": {
+      "settings": {
+        "python.defaultInterpreterPath": "${workspaceFolder}/venv/bin/python",
+        "python.terminal.activateEnvironment": true,
+        "files.associations": {
+          "*.oaf": "openagentflow"
+        }
+      },
+      "extensions": [
+        "openagentflow.openagentflow-support",
+        "ms-python.python",
+        "ms-python.vscode-pylance",
+        "esbenp.prettier-vscode"
+      ]
+    }
+  },
+  "postCreateCommand": "npm install && npm run setup",
+  "remoteUser": "vscode"
+}

README.md

@@ -40,3 +40,10 @@ Welcome! This template repository lets you instantly build, test, and compile mu
    # macOS/Linux: source venv/bin/activate
    python triage_app.py
    ```
+
+## 🐳 Dev Containers & GitHub Codespaces
+
+This repository includes a preconfigured **Development Container** (`.devcontainer/devcontainer.json`).
+- **VS Code**: Install the [Dev Containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers), open the project, and select **Reopen in Container**.
+- **GitHub Codespaces**: Open this repo in Codespaces for an instant, zero-setup browser environment with Node 22, Python 3.11, `venv`, and OpenAgentFlow extensions ready out of the box!
+